Protective casing component and an element for forming a protective casing component

ABSTRACT

A protective casing base component adapted to act as a base part of an optical fibre splice enclosure of the type including a generally tubular housing having an open end and a closed end and including means for sealing the enclosure including means for sealing the open end of the housing to the said casing component so that a plurality of optical fibre cables can pass into and out of the enclosure in use through an opening in the said component for the individual optical fibres in the cables to be spliced or connected to other such optical fibres within the enclosure, characterised in that the casing component is formed in such a way that it can be positioned or removed from a cable or plurality of cables at an intermediate point along the length thereof without interrupting the continuity of the cables, and having means for sealing the interior of the enclosure from external agencies.

The present invention relates generally to a protective casing componentand particularly to an element for forming a protective casingcomponent.

The present invention finds particular application in the field ofoptical fibre telecommunications technology.

Where it is necessary to join or splice optical fibres this is usuallydone in a rack or frame within the interior of a building protected fromthe elements. There are, however, some circumstances where it isnecessary to form splices in optical fibres outside buildings, and inthese circumstances it is known to use enclosures which protect thesplices from the effects of weather and other atmospheric agents such asmoisture, dust etc.

Optical fibres for use in telecommunications systems are generallygrouped together in bundles separated from one another by protectivesheaths, and these sheaths, sometimes referred to as “loose tubes” arethemselves grouped together within an outer cable casing. One cable may,for example, comprise 16 loose tubes, with each loose tube enclosing aplurality, for example 12, optical fibres. The maximum of the enclosureis thus 192 fibres (16×12). The total cable capacity is 6 cables perenclosure.

Optical fibre splice enclosures of the “freestanding” type, that ishousing splices made in the field at a point remote from a network nodewhich may comprise a rack of shelves in a frame or cabinet housed in abuilding, may be buried underground (where the optical fibres arelocated in ducting) or the cables may be brought up to a post to whichthe optical fibre splice enclosure may be fitted for easier access. Ineither circumstance there is occasionally a risk that the enclosurecasing may become damaged or broken either because of its exposedlocation on a pole or, even if buried, because of the effects of groundmovement, traffic passing above the duct, or too-close working ofexcavation equipment.

It will be appreciated that the very large number of splices containedwithin a single optical fibre splice enclosure constitute a logisticalproblem if the entire enclosure needs replacement. In the first placethe communications network may have a so-called “lifeline” status,meaning that certain of the connections must not be disrupted, oralternative connections must be put in place before they can beseparated. However, in the prior art optical fibre splice enclosures,the necessity for sealing the interior of the enclosure, and thereforefor the cables to pass through a sealed opening, has necessarilyresulted in the need for separation of all the splices and remaking ofthese if a splice enclosure becomes damaged and needs replacement.

It will be appreciated at this point that the enclosure is a robustprotective element which protects the delicate interior structure of thesplice couplings from physical damage as well as from the elements.Damage to the casing which is sufficient to prevent it from continuingto perform its function of protecting the interior of the casing fromthe elements may, however, occur without resulting in damage to theinterior components so that replacement of the casing, althoughnecessary in order to maintain protection from the elements, isnevertheless an entirely tedious and laborious operation due to thenecessity of unmaking all of the splice connections in order to withdrawthe optical fibre cables through the openings in the casing, and thenremaking of more splice connections in a new enclosure.

The present invention seeks to provide a solution in which the problemof replacement of broken optical fibre splice enclosure casings can bemitigated at least to some extent by allowing replacement of anenclosure casing without requiring the expensive, time-consuming, andlaborious operations involved in breaking and remaking the spliceconnections.

According to one aspect, the present invention, a protective casing basecomponent adapted to act as a base part of an optical fibre spliceenclosure of the type including a generally tubular housing having anopen end and a closed end and including means for sealing the enclosureincluding means for sealing the open end of the housing to the saidcasing component so that a plurality of optical fibre cables can passinto and out of the enclosure in use through an opening in the saidcomponent for the individual optical fibres in the cables to be splicedor connected to other such optical fibres within the enclosure,characterised in that the casing component is formed in such a way thatit can be positioned or removed from a cable or plurality of cables atan intermediate point along the length thereof without interrupting thecontinuity of the cables, and having means for sealing the interior ofthe enclosure from external agencies.

The protective casing component of the present invention may comprisetwo parts which can be secured together around the fibre or fibre cablesto be enclosed.

In an alternative embodiment, however, the protective casing componentcomprises a single element having a longitudinal slot or slit in thewall thereof through which an intermediate part of an optical fibre orfibre cable can be passed laterally thereof, the said wall being atleast partly flexible and/or resilient and the said casing sealing meansincluding means for sealing the said longitudinal slit or slot in aclosure condition.

In embodiments of the invention in which the protective casing componentcomprises two parts, the said two parts of the component (or inembodiments comprising a single element with a longitudinal slot, theparts thereof on either side of the said slit or slot) are held togetherby fixing means extending transversely of the facing edges of the twoparts or of the slit or slot.

The protective casing component of the invention may, moreover,alternatively comprise a plurality of elements which can be assembledtogether to form a composite component sealed against the ingress ofexternal agents.

The present invention may be embodied in a protective casing componentin which the elements thereof and/or the facing edges of thelongitudinal slit or slot thereof, are sealed together by gel elementsinterposed between cooperating facing surfaces of the parts of thecomponent.

In a preferred embodiment of the invention the component is the basepart of an optical fibre splice enclosure including a generally tubularhousing having an open end and a closed end, and means for sealing theopen end of the housing to the closed or assembled casing component.

In such an embodiment the component may comprise a semi-cylindrical bodyhaving a generally radial flange at one end thereof and two generallylongitudinal edges in the face of one of which there is an axiallyextending channel and in the face of the other of which there is acooperating axially extending ridge which projects into the channel whenthe two such elements are fitted together.

An element as defined hereinabove may have an annular skirt portionextending axially away from the said radial flange to form a seat forsealant gel between the casing component formed from two such elementsand the open end of a tubular housing.

An element formed according to this aspect of the present invention mayalso be so configured that the said axial groove in the face of onelongitudinal edge communicates with the seat region defined by the saidradial flange of the said annular skirt portion of the element to allowa continuous bead of gel to extend around the annular region of the endof the component and axially along the interface between the twoelements of which it is composed.

The present invention also comprehends an optical fibre splicingenclosure comprising a casing component (which may be made from casingcomponent elements as hereinabove defined) in the form of a base for agenerally tubular housing which can be sealed to one end of thecomponent and a gel block which can be fitted in the other to allowsealed entry and exit of optical fibre cables to and from the interiorof the enclosure.

There may further be provided one or a plurality of optical fibreorganisers within the sealed interior of the fibre splice enclosure,formed by assembly of the housing to the base and sealing thereof.

One embodiment of the present invention will now be more particularlydescribed, by way of example, with reference to the accompanyingdrawings, in which:

FIG. 1 is a perspective view, dismantled, of a prior art optical fibresplice enclosure of the type to which the present invention relates;

FIG. 2 is an exploded view of a component constituting an embodiment ofthe present invention comprising two elements; and

FIG. 3 is a perspective view of the component of the present inventionwith the two elements thereof fitted together.

Referring first to FIG. 1, an optical fibre splice enclosure of knownform comprises a generally cylindrical outer envelope or casing 11within which is housed a fibre splice organiser generally indicated 12comprising a plurality of individual fibre splice connectors 13 and aplurality of storage trays 14 for overlength fibre, hinged inassociation therewith so that the surplus or overlength of optical fibreneeded to allow changes to be made to the connections after its firstinstallation, can be stored tidily.

As explained above, the optical fibres are housed in bundles withinloose tubes which are themselves located within optical fibre cablessuch as the cables 15 illustrated in FIG. 1. Access to the fibresinvolves removal of a section of the cable sheath to enclose the exposedloose tubes, followed by partial or complete removal of the tube wall ofone or more of the exposed loose tubes to reveal the enclosed opticalfibres. The removal of the tube wall is commonly called “shaving” thetube, this being a necessarily delicate operation requiring care toavoid damage to the revealed optical fibres. The exposed lengths ofoptical fibres are housed on the overlength storage trays 14.

The tubular casing 11 has a closed end 16 and an open end 17, and theentire organiser 12 is introduced into its interior through the open end17. This open end is sealed to a base 18 which comprises a generallycylindrical body 19 having a radial flange 20 which contacts and issealed to the open end of the enclosure tube 17. The tubular body 19houses a gel block generally indicated 21, one example of which is shownoutside the base 18 in FIG. 1 (although the interior of the base 18 isalso shown housing a gel block through which the optical fibre cables 15pass into the interior of the enclosure tube 11.

As will be appreciated, if the casing 11 becomes cracked or broken it isa simple matter to remove this and replace it with another, reinstatingthe seal between the open end 17 and the flange 20 of the base 18. If,however, the base 18 itself becomes damaged there is no way in which anew base can be fitted without separating all the optical fibre splicesto allow axial withdrawal of the optical fibre cables 15 through the gelblock 21 housed in the base 18 itself. In communications networks wherethe optical fibres 15 have “lifeline” status this cannot be done withoutproviding duplicated connections to cover the period of disconnection ofthe optical fibres. The very large number of fibres and the potentialfor subsequent misconnections when the splices are remade is evident.

FIG. 2 illustrates an embodiment of the invention which allowsreplacement of the base 18 without requiring separation of all thesplices on the splice block 13. This base 18 comprises, like the priorart base, a tubular body 19 having a radial flange generally indicated20. In this embodiment, however, the base 18 is formed in two parts 18a, 18 b each identical to one another and each comprising asemi-cylindrical body portion 19 a, 19 b having flat axially extendingedge faces 21, 22 (only the edge faces 21, 22 b of the semi-cylindricalportion 19 b being visible in FIG. 2.

Projecting radially from the semi-cylindrical body 19 a, 19 b and flushwith the edge faces 21, 22 are respective pairs of lugs 23, 24 and 25,26. Each lug is pierced by a respective hole 23 b′, 24 b′, 25 b′, 26 b′.At one axial end of the semi-cylindrical body 19 is a conically taperedportion 27 from the free edge of which projects a radial flange 28 and aradially outer axial skirt 29. A second, radially inner axial skirtportion 30 projects parallel to the axial skirt 29 from a root portionof the conical portion 27.

At the other end of the semi-cylindrical body 19 from that bearing theconical portion 27 is a small radially inwardly directed lip 31 againstwhich, in use, engages a gel block such as the block 21 illustrated inFIG. 1. The flat edge face 21 b of the semi-cylindrical body 19 b bearsa projecting ridge 33 and this ridge extends into the conical portion27, terminating at an outer end 34 close to the junction between theradial flange 28 and the radially outer axial skirt 29. The other flatedge face 22 b of the semi-cylindrical body 19 b has a channel 35 ofsimilar shape extending along the length of the flat edge face 22 b andthe corresponding end face of the conical portion 27, terminating at thejunction region between the radial flange 28 and the radially outeraxial skirt 29, and in communication with a circumferential groove 36 bwhich extends around the radial flange 28 at the root thereof.

The groove 35 has a laterally open region 35′ on the inner face of thesemi-cylindrical body 19. This enables the gel in the groove 35 to makedirect contact with the gel of the gel block housed in the cylindricalportion of the base 18, engaging against the radial inner lip 31.

In use, the two parts 18 a, 18 b of the base 18 can be fitted togetherover an existing, known type of gel block (not shown, but which may belike the gel block 21) bearing existing optical fibre cables 15 andconnected to a fibre splice assembly such as that represented by thereference numbers 12,13, 14 in FIG. 1, without requiring any dismantlingor breaking of the connections formed by the splices. The twosemi-cylindrical parts 19 a, 19 b are held together by bolts passingthrough the openings 23′, 24′, 25′, 26′ in the lugs 23, 24, 25, 26, withgel sealant located in the groove 35 to which pressure is applied by theridge 34 as the bolts are tightened. Two further lugs 38, 39 with holes38′, 39′ are located at the junction region between the semi-cylindricalbody 19 and the conical portion 27 in order further to improve the axialseal formed by the ridge 34 engaging in the groove 35.

Once the two parts 18 a, 18 b have been fitted and sealed together andthe bolts tightened, the base 18 can be used in the same way as aconventional base as illustrated in FIG. 1, with a cylindrical cover 11being mounted thereto, engaging in the groove 36, which may also beprovided with gel sealant to seal the open end 17 of the tubular casing11 in place on the base 18.

The radially inner axial skirt 30 has a plurality of bosses 42 throughwhich pass axial openings 42′ for receiving axial bolts to secure thecylindrical casing 11 by means (not shown) so as to tighten the rim 17of the open end of the cylindrical casing 11 into the gel in the groove36. The communication between the groove 35 and the groove 36 ensuresthat the axial beads of sealant gel which seal the longitudinallyextending edge faces 21, 22 together forms an essentially continuousseal with the circumferential bead of gel in the groove 36 so that thisjunction is not a point of potential entry of atmospheric contaminants.

1. A protective casing base component adapted to act as a base part ofan optical fiber splice enclosure of the type including a generallytubular housing having an open end and a closed end so that a pluralityof optical fiber cables can pass into and out of the enclosure in usethrough an opening in the said component for the individual opticalfibers in the cables to be spliced or connected to other such opticalfibers within the enclosure, wherein the casing component is formed insuch a way that it can be positioned or removed from a cable or aplurality of cables at an intermediate point along the length thereofwithout interrupting the continuity of the cables, and in that thecasing component has means for sealing the interior of the enclosurefrom external agencies including means for sealing the open end of thehousing to the said casing component.
 2. A protective casing componentas claimed in claim 1, comprising two parts which can be securedtogether around the fiber cables to be enclosed.
 3. A protective casingcomponent as claimed in claim 1, comprising a single element having alongitudinal slit or slot in the wall through which an intermediate partof an optical fiber can be passed laterally thereof, the said wall beingat lest partially flexible and/or resilient and the said casing sealingmeans including means for sealing the said longitudinal slit or slot ina closure condition.
 4. A protective casing component as claimed in clam2, in which the said two parts of the component or the parts thereof oneither side of the said slit or slot are held together by fixing meansextending transversely of the facing edges of the two parts or of theslit or slot.
 5. A protective casing component as claimed in claim 1,comprising a plurality of elements which can be assembled together toform a composite component sealed against the ingress of externalagents.
 6. A protective casing component as claimed in claim 1, in whichthe elements of which it is composed and/or the facing edges of thelongitudinal slit or slot are sealed together by gel elements interposedbetween cooperating facing surfaces of the parts of the component.
 7. Aprotective casing component as claimed in claim 1, in which thecomponent is installed as the base part of an optical fiber spliceenclosure.
 8. An element for forming a protective casing component asclaimed in claim 1, comprising a semi-cylindrical body having agenerally radial flange at one end thereof and two generally parallellongitudinal edges in the face of one of which there is an axiallyextending channel and in the face of the other of which there is acooperating axially extending ridge which enters the channel when twosuch elements are fitted together.
 9. An element as claimed in claim 8,in which there is an annular skirt portion extending axially away fromthe said radial flange to form a seat for a sealant gel between a casingcomponent formed from juxtaposition of two such elements and the openend of a tubular housing.
 10. An element as claimed in claim 8, in whichthe said axial groove in the face of one longitudinal edge communicateswith the seat region defined by the said radial flange and the saidannular skirt portion of the element to allow a continuous bead of gelto extend around the annular region at the end of the component andaxially along the interface between the two elements of which it iscomposed.
 11. An optical fiber splice enclosure comprising a casingcomponent as claimed in claim 1, in the form of a base for a generallytubular housing which can be sealed to one end of the component, and agel block which can be fitted in the other to allow sealed entry andexit of optical fibers cables to and from the interior of the enclosure.12. An optical fiber splice enclosure as claimed in claim 11, in whichthere is or are further provided one or a plurality of optical fiberorganizers within the sealed interior formed by assembly of the housingto the base.
 13. An optical fiber splice enclosure comprising a casingcomponent composed of two elements as claimed in claim 8, in the form ofa base for a generally tubular housing which can be sealed to one end ofthe component, and a gel block which can be fitted in the other to allowsealed entry and exit of optical fibers cables to and from the interiorof the enclosure.
 14. An optical fiber splice enclosure as claimed inclaim 13, in which there is or are further provided one or a pluralityof optical fiber organizers within the sealed interior formed byassembly of the housing to the base.
 15. An optical splice enclosureformed using the component as claimed in claim 1.